1. Field of the Invention
The invention relates to the area of high temperature superconductors, in particular to a ceramic high temperature superconductor in bulk form, and a method of manufacturing same.
2. Discussion of the Background
Recently there has been an unprecedented intensification of the development of superconductors, due to the discovery of high temperature superconduction in ceramics of the La-Ba-Cu-O system, leading to the development of a series of ceramics with increasing critical temperatures.
Some of these known novel ceramics can be produced in bulk form; others only in the form of thin layers. For applications in electrical engineering, it is important to have a superconductor in the bulk form.
Substantial known research in the art has been devoted also to the system Y-Ba-Cu-O. One material of this type, the oxide YBa.sub.2 Cu.sub.3 O.sub.7-.delta., which is known under the designation "1-2-3 compound", is distinguished by a critical temperature T.sub.c of about 90.degree. K. and may be produced in bulk form relatively easily. Accordingly it is of particular interest for the intended superconductors.
However, the "1-2-3 compound" presents the problem that the oxygen in the material is not thermally stabile. At a few hundred .degree. C. there are undesired structural changes, resulting in breakdown of the ceramic material and modification of the superconducting properties of the material.